The Windows Communication Foundation (WCF) is a framework developed by Microsoft for building service-oriented applications. It allows developers to create distributed systems that are reliable, secure, and interoperable by enabling them to build applications that communicate with each other through various protocols.

WCF is a part of the .NET Framework, and it provides a unified approach to building distributed systems. With WCF, developers can create applications that communicate with other applications irrespective of the platform, technology or programming language. WCF supports several communication protocols, including HTTP, TCP, and Peer-to-Peer network, and allows messages to be transferred using different data formats such as Text, Binary, and XML.

One of the benefits of WCF is that it provides a simplified programming model, which makes it easier for developers to create distributed applications. WCF also provides a set of tools that simplify the creation, deployment, and management of services. For instance, developers can use the WCF Service Configuration Editor to configure a service endpoint, or the WCF Test Client to test a service method.

WCF also supports different security mechanisms such as transport-level security and message-level security, which allows developers to secure their services against unauthorized access. Additionally, it provides different hosting options, which includes IIS hosting, Windows service hosting, and self-hosting, giving developers more flexibility in choosing where to deploy their services.

With WCF, developers can create applications that provide various types of services, such as Web services, RESTful services, and SOAP services. A Web service provides a way to expose functionality over the internet, while a RESTful service uses HTTP as the communication protocol and supports resources which can be accessed and manipulated using HTTP verbs. On the other hand, a SOAP service uses XML to define the message format and allows applications to communicate using different protocols.